1. Field of the Invention
The present invention relates to an information recording apparatus for recording information onto the hard disk of a hard disk drive, etc., used for a computer.
2. Related Background Art
FIG. 1A is a plan view showing a conventional hard disk drive 1, wherein a hard disk D with its surface onto which a magnetic recording medium is vapor-deposited is always rotated about a spindle 2 at a high speed. An unillustrated magnetic head incorporated into a slider 3 taking a substantially rectangular Parallelepiped shape is disposed in close proximity to the surface of the hard disk D. The slider 3 is secured to a tip of a magnetic head arm 5 having a center-of-rotation 4 outside the hard disk D. A voice coil 6 is fixed to a proximal end of the magnetic head arm 5.
In this construction, the magnetic head relatively moves in a substantially radial direction on the hard disk D and makes a circular-arc movement in combination with the rotating hard disk D. The magnetic head is thus capable of writing magnetic information on a track in an arbitrary position on the surface of the hard disk D assuming a disc-like configuration and reading the magnetic information from the track at the arbitrary position.
The hard disk D is divided into a plurality of circular tracks each having a different radius, which are defined as circles concentric to the center-of-rotation 4, and each track is also segmented into a plurality of circular arcs. Recording and reproducing processes are executed in time-series in the peripheral direction with respect to the plurality of finally segmented circular arc areas, thus effecting magnetic recording on the hard disk D.
In recent years, a recording capacity of the hard disk D and a density of recording information have been required to increase. To meet those requirements, there is a necessity for enhancing the recording density in the radial direction by narrowing track widths on the concentrically, circularly divided hard disk D. The recording density in the radial direction is expressed in a track density T/I (track/inch) and is presently on the order of 8000 T/I, which indicates that a track interval is approximately 3.125 .mu.m.
A process of seeking out such a minute track pitch involves positioning a slider 3 as a magnetic head by 0.06 .mu.m in the radial direction on the hard disk D, which value is defined as a resolution on the order of 1/50 of the track width, and writing a servo track signal in advance. For this purpose, the servo track signals must be sequentially written while executing a high-resolution positioning process for a short period of time.
FIG. 1B is a perspective view showing a hard disk drive 1 for writing the servo track signal by use of a push rod 7. A cylindrical surface of the push rod 7 is kept in contact with a lateral surface of a magnetic head arm 5, and the push rod 7 is attached to an arm 9 including a rotary shaft 8 coaxial with the center-of-rotation 4. Then, a rotary positioner or the like consisting of a rotary encoder 10 and a drive motor 11 is fixed to the rotary shaft 8. An output of the rotary encoder 10 sequentially is connected to a signal operation processing portion 12, a motor driver 13 and a drive motor 11.
The positioning process is implemented by sequentially minutely moving the push rod 7 while pushing the magnetic head arm 5 against the cylindrical surface of the push rod 7 in the horizontal direction, thus writing the servo track signals in sequence. The push rod 7 is capable of performing the positioning process and the minute movement with a resolution and precision as high as 0.01 .mu.m or under by use of the rotary positioner.
In contrast with this, there has been recently devised a system for executing the minute movement in a non-contact manner for correspondence to high-density recording. FIG. 1C is a perspective view showing a hard disk drive of a non-contact interference distance measuring system. A retroreflector 14 like a corner cube is placed on a magnetic head arm 5. A beam splitter 15 and a laser light source 16 are arranged on the optical axis of a light beam L1 irradiating this retroreflector 14. A fixed mirror 17 for reflecting a light beam L2 is disposed on one side in a reflecting direction of the beam splitter 15, while, on the other side, a light receiving element 18 for receiving the light beam L2 is disposed. Then, an output of the light receiving element 18 is connected to a voice coil 6 via a signal operation processing portion 19 and a voice coil motor driver 20.
A laser beam emitted from the laser light source 16 is split into two light beams L1, L2 by the beam splitter 15. The light beam L1 is reflected by the retroreflector 14, and the light beam L2 is reflected by the fixed mirror 17. Both of the light beams L1, L2 reach the beam splitter 15, and overlapped interference light beams are received by the light receiving element 18. A signal thereof is arithmetically processed in the signal operation processing portion 19, thereby measuring a position of the magnetic head arm 5 at a high precision. Based on this piece of data, the voice coil motor driver 20 flows an electric current through the voice coil 6 to directly move the magnetic head arm 5. Thus, a high-precision positioning process is implemented in a non-contact manner by carrying out the proper control.
In the non-contact high-precision positioning system based on the principle of a laser interference distance measurement in which a movement of the magnetic hard arm 5 is measured by an optical means without mechanically pushing the magnetic head arm 5, there might be a necessity for placing the corner cube for sticking the retroreflector 14 defined as an optical index onto the magnetic head arm 5, and a problem lies in securing a space and in a variation in gap between the slider 3 and the hard disk D due to an increase in weight.
Further, it also can be devised that the distance to the lateral surface of the slider 3 is directly optically measured by adding nothing to the magnetic head arm 5. However, if the light beam for measurement comes in and out from outside in parallel to the hard disk D, some contrivances are required, wherein a lateral surface of the hard disk drive 1 is normally formed with a window for transmitting the light beam, or a lay-out is made so as not to intercept the light beams with electronic parts, etc. Accordingly, it can be devised that the light beam falls substantially in a direction of an upper surface of the hard disk D by deflecting the light beam by 90 degrees, using a small mirror and a prism.
The slide 3 is, however, approximately 300 .mu.m in thickness, and a gap from the surface of the hard disk D is approximately 1 .mu.m. Therefore, in a simple 45-degrees mirror or 45-degrees deflection prism having an angle of several millimeters, the light beam is required to come in and out in the vicinity of a front edge of the mirror, and the prism must be manufactured with an allowance because of an acute angle of the mirror edge. Further, there might be a possibility in which the mirror edge impinges upon the surface of the hard disk D. Moreover, the lateral surface of the slider 3 has just a rectangular area as minute as 1000.times.300 .mu.m, and hence, there arises such a problem that a sectional configuration of the illumination light must be formed in a small rectangular or elongate elliptical shape corresponding thereto in order to effectively obtain the reflected light.